Catalytic synthesis of acrylonitrile from olefins, ammonia and oxygen



United States Patent M 3 262,962 CATALYTIC SYNTHlESIS OF ACRYLONITRILE FROM OLEFINS, AMMONIA AND ()XYGEN Edgar L. McDaniel and Howard S. Young, Kingsport,

Tenn., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Jan. 23, 1961, Ser. No. 83,916

6 Claims. (Cl. 260465.3)

This invention relates to the preparation of aliphatic unsaturated nitriles, and more particularly acrylonitrile, by a novel and improved method wherein an olefin, ammonia and oxygen are reacted together in the vapor phase, in the presence of a particular catalyst comprising bismuth and certain inorganic heteropoly acids.

It is known that unsaturated nitriles can be prepared by reacting olefins with ammonia under oxidizing conditions at elevated temperatures. For example, I. N. Cosby in U.S. Patent No. 2,481,826, issued September 13, 1949, describes the preparation of lower aliphatic nitriles such as acrylonitrile, methacrylonitrile and acetonitrile by reacting an olefin such as propene, butene-l, etc. with ammonia and oxygen, at 400600 C., in the presence of various oxidation catalysts and especially vanadium oxides containing molybdenum oxide. Where propene Was used as the starting olefin, yields not exceeding about 6 mole percent (Example 6) of acrylonitrile and a substantial amount (10 mole percent) of hydrogen cyanide were obtained. In J. D. Idol, In, US. Patent No. 2,904,- 580, issued September 15, 1959, a vapor phase method is also described for preparing acrylonitrile, wherein a mixture of propylene, ammonia and oxygen is passed over a catalyst comprising the bismuth, tin, and antimony salts of phosphomolybdic and molybdic acids and bismuth phosphotungstate. This process is stated to require not only careful control of the surface area of the catalyst and pressure conditions, but the amount of water employed is a critical factor.

We have now found that by reacting propylene, ammonia and oxygen at elevated temperatures, in the presence of a catalyst comprising bismuth and an inorganic heteropoly acid or salts thereof, and more especially a catalyst comprising in effect a mixture of essentially of bismuth oxide and dodecamolybdoceric acid, that the reaction goes smoothly to a relatively higher conversion to the principal product acrylonitrile, and to a considerably lesser amount of acetonitrile, with a minimum of by-products as compared with prior art processes such as mentioned above, and that water is not critical to operability of the process of this invention, since excellent activity and selectivity can be obtained without water diluent.

It is, accordingly, an object of the invention to provide a novel and improved method for the synthesis of aliphatic unsaturated nitriles wherein a carbon-to-carbon double bond is conjugated with the carbon-to-nitrogen triple bond, and in particular acrylonitrile.

Another object is to provide a novel process for converting propylene to acrylonitrile in high conversion and high yield in a continuous process. Yet another object is to convert olefins to nitriles while maintaining the olefinic bond in the alkyl moiety of the nitrile.

An object of the invention is to provide a means of converting propylene to acrylonitrile by use of a bismuth and dodecamolybdoceric acid catalyst. A further object of the invention is to provide a means of converting olefins to IE-unsaturated nitriles by use of a bismuth and dodecamolybdoceric acid catalyst. Another object is to introduce nitrogen from ammonia into organic compounds by use of a bismuth and dodecamolybdoceric acid catalyst.

It is also an object of the invention to provide a method for synthesizing acrylonitrile without the use of such 3,262,962 Patented July 26, 1966 hazardous and toxic chemicals as hydrogen cyanide, acetylene, and ethylene oxide.

Another object of the invention is to provide a process of converting propylene, ammonia and oxygen into acrylonitrile over a bismuth and dodecamolybdoceric acid catalyst wherein the conditions of the process may be varied over wide ranges. It is a further object of the invention to provide a means of producing acrylonitrile with the simultaneous production of large quantities of heat which may be recovered and utilized.

A further object of the invention is to provide a novel catalyst comprising bismuth and dodecamolybdoceric acid for the conversion of propylene, ammonia, and oxygen to acrylonitrile. Another object of the invention is to provide a bismuth and dodecamolybdoceric acid catalyst for the conversion of methyl groups attached to olefinic carbon atoms into nitrile groups.

Other objects will become apparent from the description and examples hereinafter.

In accordance with the invention, we prepare unsaturated aliphatic nitriles, and more especially acrylonitrile, by passing a feed mixture comprising a short-chain olefin containing from 3-5 carbon atoms such as propylene, butylene, 2-methylbutene-1, etc., ammonia and oxygen, in vapor phase at elevated temperatures, over a catalyst comprising bismuth and an inorganic heteropoly acid. The preferred process is the conversion of propylene to acrylonitrile employing bismuth oxide or a bismuth compound convertible with heat to the oxide with dodecamolybdoceric acid. The reaction is illustrated below with propylene.

A minor proportion of acetonitrile is also formed. The ratios of reactants may be widely varied from the theoretical mole ratios of propylenezoxygenzammonia of 1:1 /2:1. We prefer ratios near these values; however, the process is operable at propylenezoxygen ratios from as low as 11005 to those as high as 1:10 and propylene:ammonia ratios as low as 120.05 to those as high as 1:10, i.e. from 0.0510.0 moles of ammonia and from 0.0510.0 moles of oxygen per mole of the olefin. Both propylenezoxygen and propylene:ammonia ratios may be varied from the theoretical ratios. Water may be fed to the reactor, or it may be omitted. Water acts as a diluent and, when used, the preferred amounts range from 0.052.0 moles per mole of the propylene in the feed. Nitrogen may be fed to the reactor. This has no particular effect upon the chemistry involved, but has the practical advantage that since nitrogen is not detrimental, air may be used as the source of oxygen. If air is used, the ratio of oxygen to nitrogen will be approximately 1:4. The temperature of the reaction can also be varied within the limits of about 300600 C., but preferably in the range of about 400-550" C. The reaction is also not significantly pressure dependent. For example, it may be operated satisfactorily at atmospheric pressures, which condition is preferred, but lower or sub-atmospheric pressures and higher or super-atmospheric pressures may also be used to give generally similarly good results. The choice of operating pressures may be governed by economic considerations. The gaseous hourly space velocity (GHSV) may also be varied over a wide range, for example, values (S.T.P.) as low as may be used, and values as high as 6000 may be used. The preferred space velocity is in the range of about -1000. The catalyst may be used either in a fixed bed or in fluidized state. In the latter case, the catalyst exists as small particles which are suspended in an upflowing stream of reactant gases. The latter method of carrying out the invention otters advantages such as, for example, superior temperature control, and less explosive hazard. Water may be included, if desired, although this is not critical for the reaction goes well without such addition. Oxygen may be fed in elemental form or as air. Also, inert gases such as nitrogen, argon, etc. can be admixed with the oxygen.

In general, any type of apparatus that is suitable for carrying out the process of the invention in the vapor phase may be employed, e.g., a tubular type of reactor or furnace which can be operated in continuous or intermittent manner and is equipped to contain the catalyst in intimate contact with the entering gases. The reacted gases are then conducted to suitable cooling and separatory equipment and the products further separated and recovered by any of the methods known to those skilled in the art. For example, one such method involves scrubbing the effluent gases from the reactor with cooled water or an appropriate solvent to remove the products of the reaction. In such case, the ultimate nitrile products may be separated by conventional means such as distillation of the resulting liquid mixtures. Unreacted ammonia and olefin may be recovered and recirculated through the system. Spent catalyst may also be reactivated by heating in contact with air.

The composition of the catalyst is all-important. Bismuth salts such as bismuth nitrate which decompose under the conditions of the catalyst preparation presumably to bismuth oxide (Bi O are used as a promoter. With this is mixed a heteropoly acid, e.g., the preferred dodecamolybdoceric acid of the probable formula and the mixture then calcined at 450-600 C. for several or more hours. Actually, the ammonium salt of this acid is used because it is more easily prepared than the free acid and is believed to decompose to the free acid under the high temperatures achieved in the calcination step. A key portion of the invention resides in the incorporation of the heteropoly acid into the catalyst composition in the form of its ammonium salt. The concentrations of the bismuth component and the heteropoly acid component may each vary from about 3 percent to 75 percent by weight of the catalyst.

Other heteropoly acids and ammonium salts thereof which may be used in preparing the catalysts of the invention are represented by the following general formula:

wherein X represents besides the mentioned cerium atom other rare earth atoms of the cerium group such as lanthanum, praseodymium, neodymium, samarium, etc. and other rare earths of the yttria group such as gadolinium, etc. or mixtures thereof. Compounds of this kind are described by C. G. Grosscup, J. Amer. Chem. Soc., 52, pages 5154-60 (1930). While molybdenum is shown as the coordinating element, it will be understood that other elements including the vanadium and chromium families of elements can be substituted for the molybdenum to form generally similar heteropoly acids, for example, vanadium, niobium, tantalum, chromium, tungsten and uranium. In addition, more than one of these elements may serve as coordinating elements in the heteropoly acid, and when more than one element serves as coordinating atoms, molybdenum may be included. The above acids may likewise be mixed with bismuth salts or oxide in the mentioned proportions, calcined as indicated and reduced to operable granules or particles.

In all of the following examples, exactly the same conventional equipment was employed for carrying out the reaction of the invention, as well as other reactions for comparative purposes, including the separation of the products from the effluent gases by scrubbing with water and their ultimate separation by distillation. The products were analyzed by conventional analytical procedures.

active and selective for the synthesis.

The definitions as used in the examples and Table I are defined as follows:

The percent conversion to acrylonitrile may be based on propylene or on ammonia.

Based on propylene, percent conversion:

moles acrylonitrile formed moles propylene fed X for any cut Based on ammonia, percent conversion= moles acrylonitrile formed moles ammonia fed X100 The yield may be calculated based on propylene or on ammonia.

Based on propylene, percent yield:

moles acrylonitrile formed total moles propylene consumed Based on ammonia, percent; yield= moles acrylonitrile formed total moles ammonia consumed EXAMPLE 1 A catalyst comprising 37 percent bismuth oxide and 33 percent dodecamolybdoceric acid on silica was prepared thusly: 400 g. of an aqueous silica sol which was 30 percent SiO was placed in a beaker equipped with a power stirrer and situated on an electric hot plate. Then 151 g. of ammonium dodecamolybdocerate crystals was pulverized with a porcelain mortar and pestle. The powdered ammonium dodecamolybdocerate was slowly added to the vigorously stirred silica sol, which resulted in a canary yellow slurry. The stirred slurry was heated to the boiling point, and a solution of 308 g. of bismuth nitrate in 220 ml. of dilute aqueous nitric acid was added slowly to the hot mixture. After additional heating and stirring, the mixture thickened. It was transferred to an evaporating dish and dried in an oven at C. The preparation was then calcined four hours at 500 C. in a mufile furnace. The resulting catalyst was crushed, and a 40 x 100 mesh range of particles was taken. Two hundred milliliters of this was charged to a laboratory-scale fluidized solids reactor. The data shown in Table I were then taken for a series of runs. The catalyst was quite Minor concentrations of acetonitrile and hydrogen cyanide were also formed.

Referring to the table, it will be noted that a yield as high as 70 mole percent of acrylonitrile, based on the propylene consumed was obtained at a temperature of 485 C., and a space velocity of 720, employing a feed mixture in the mole ratios of 1 mole of propylene to each 1.5 moles of oxygen, each mole of ammonia, each mole of water and each 6 moles of nitrogen. The conversion to acrylonitrile was 47.9 mole percent, while the conversion to acetonitrile was only 7.3 mole percent. Lower reaction temperatures resulted in lower conversions, for example, 28.7 mole percent of acrylonitrile at 460 C., while the conversion to acetonitrile increased slightly to 8.5 mole percent. However, all of the runs represent satisfactory operating conditions. As indicated previously, the water can be dispensed with entirely, if desired, without materially affecting the conversion an yield values for acrylonitrile.

EXAMPLE 2 This example illustrates the adverse results obtained when only silica is used as the catalyst in the vapor phase reaction of propylene, ammonia and oxygen.

6 EXAMPLE 5 A catalyst comprising 35.9 percent cerous molybdate (Ce (MoO and 35.4 percent bismuth oxide on silica was prepared as follows: 104.5 g. of ammonium hepta- A sample of silica sol (30 percent SiO in H O) was 5 .molybdate was dissolved in 1500 ml. of distilled water and evaporated in an evaporating dish on a steam bath and the solution was filtered. Then a filtered solution of 147 then was dried in an oven at 130 C. After calcination g. of CeCl in 400 ml. of distilled water was slowly added at 500 C. for four hours, 200 ml. of 40 x 100 mesh silica to the stirred molybdate solution. The resultant finely was charged to a laboratory fluidized solids reactor. This divided yellow precipitate was collected on a Buchner material was tested at 450 C., with a propylenezoxygen: 1O funnel. The precipitate was slurried with 500 ml. of ammoniazwaterznitrogen mole ratio of 1:1 /2:1:1:6, and distilled water and again collected on a Buchner funnel. a GHSV of 630. This material was almost inert, pro- It was then slurried with 200 ml. of distilled water and this ducmg no n1tr1le and allowmg only a small amount of slurry w l l dd d t 400 g f ili 1 (30 Propylene to be f to 2 and zQ- a cent SiO with stirring. The yellow slurry was heated When the Teactlon temperatllre Was Increased to 470 to the boiling point with stirring, and then a solution of h same GHSV and ratlos P reactants as before 308 g. bismuth nitrate in dilute nitric acid was added. no {mules W i f Changmg the f q i The preparation was heated with stirring until it thickiggg hqg "z a i ratios to /2 at ened. It was transferred to an evaporating dish and 1 no pro use m water was removed on a steam bath. The preparation X LE 3 was dried in an oven at 130 C. and then was calcined This example illustrates the very poor results obtained four hours at i m a muffle furnacewhen just a bismuth oxide on silica catalyst is employed TWO hundred l ht rs 0f 40 X 100 mesh catalyst was in the vapor hase reaction of propylene am nonia and r charged to a lElbOI'ZltOIY fillldlZed SOlldS reactor. The o ygen, test results are shown in Table I. This catalyst had about A catalyst comprising percent Bi O on silica was half the activity for acrylonitrile synthesis as the bismuth prepared by adding bismuth nitrate in dilute nitric acid dodecamolybdoceric acid catalyst in Example 1 above.

Table I Mole Percent Mole Percent Mole Ratio, Mole Percent Yield of Mole Percent Yield of Propylene: Conversion to Aerylonitrile Conversion to Acetonitrile Catalyst Oxygen: GHSV, Cut Acrylonitrile, Acetonitrile, Ex. Catalyst Temp, Ammonia S.'I.P. Time, Based 011 Pro Based on Pro- C. Water: Min. pylene or 011 Based Based pyleue or on Based Based Nitrogen b Ammonia on on Ammonia on on Pro- Am- Pro- Am pylene monia pylene monia 1. 37% 31 0 11115332, dodeca- 490 1:1%:1:1:6 630 30 40.7 51.0 49.8 9.1 11.4 11.1 molybdoccric acid on silica. 485 1:1%:l:l:6 720 30 47. 9 70.0 47. 9 7. 3 10. 5 7. 3 490 1;1%=1=1:6 450 30 49.7 57.3 49.7 6.0 6.9 6.0 460 1:1%;1;1:6 630 30 34.5 51.4 34.5 7.6 11.3 7.6 460 1:1%:1:l:6 720 30 23.7 46.5 23.7 3.5 13.3 8.5 460 1:2:1:1:8 630 30 39.1 58.2 39.1 7.2 10.7 7.2 470 1:1%:1:1:6 540 30 47.2 64.1 47.2 3.1 10.9 8.1 490 4 1:1%:1:0;6 650 30 38.0 63.9 44.9 6.0 8.5 7.1 3.--. 30% Bi 03 on silica 470 1:1%:1:1:6 630 28 1.3 4.1 1.8 7.1 16.0 7.1 4 33% doldecamolybdoceric acid 475 111%:1z1z6 630 30 0 0 0 7.9 14.7 9.7

011 S1 ma. 5.... 35.4% B1203 plus 35.9% eerous 490 1:1%:1:1:6 630 39 23.7 29.7 40.5 10.2 12.8 17.4 molybdate on silica. 500 1:1%:1:1:6 720 30 19.6 26.7 35.7 9.3 13.4 17.9 500 l:1%:1:l:6 450 30 21.3 25.1 31.7 14.7 17.4 22.0 490 1:1%:1:1:6 630 30 20.2 23.6 36.7 10.6 15.1 19.3

9 Water diluent was not fed for this cut.

b The oxygen and nitrogen was fed in the form of atmospheric air. solution to silica sol. The white slurry was heated with stirring on a steam bath until it thickened. It was then dried in an oven at 130 C., and calcined for six hours in an air muffie furnace at 500 C. to decompose the nitrate. r

EXAMPLE 4 This example illustrates the fact that no acrylonitrile is produced at all when the catalyst employed for the reaction of propylene, ammonia and oxygen is a catalyst devoid of bismuth oxide, i.e. comprising dodecamolybdoceric acid on silica.

A catalyst comprising 33 precent dodecamolybdoceric acid on silica was prepared from ammonium dodecamolybdocerate and silica sol in the same manner as that described in Example 1. Two hundred ml. of 40 x 100 mesh catalyst was tested in a laboratory fluidized solids reactor (see Table I). This catalyst was quite inactive for acrylonitrile synthesis. Small quantities of acetonitrile were produced.

The results as tabulated in above Table I illustrate the unusual and syngeristic effects of bismuth oxide and dodecamolybdoceric acid when combined in the catalyst. No satisfactory explanation can be given. Either component is quite inactive in the absence of the other. Undoubtedly part of the explanation lies in the porous and skeletal-like structure of the dodecamolybdoceric acid. However, even when this structure is present, an activator, i.e., bismuth, is necessary for activity to produce acrylonitrile.

While the process of the invention has been shown in the examples with specific proportions of bismuth oxide and dodecamolybdoceric acid, it will be understood that any proportions coming within the mentioned operable range will give generally similar good conversions and yields of acrylonitrile under the prescribed conditions. Also, as previously set forth the other mentioned heteropoly acids can be substituted in the process of the invention for the dodecamolybdoceric acid. Acrylonitrile is of course known to be useful as an intermediate in organic synthesis of phamaceuticals, dyes, etc., as well as being the basic component in many synthetic polymers that are useful for preparing fibers, sheets, molded objects, and the like.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

What we claim is:

1. A process for preparing a compound selected from the group consisting of acrylonitrile and acetonitrile which comprises reacting a mixture comprising propylene, ammonia and oxygen in the proportions of from 005-100 moles of the ammonia and from 005-100 moles of the oxygen to each mole of the propylene, in vapor phase at from 300600 C., in the presence of a catalyst consisting essentially of the product of the calcination of a mixture of bismuth nitrate and a heteropoly acid component selected from the group consisting of dodecamolybdoceric acid and ammonium dodecamolybdocerate, and mixtures thereof, wherein the concentration of the bismuth component is about 3% to 75% by weight of the catalyst and wherein the concentration of the said heteropoly acid component is about 3% to 75% by weight of the catalyst and thereafter separating the nitrile products.

2. A process for preparing a mixture of acrylonitrile and acetonitrile which comprises reacting a mixture comprising propylene, ammonia and oxygen in the proportions of from 005-100 moles of the ammonia and from 005-100 moles of the oxygen to each mole of the propylene, in vapor phase at from 300600 C., in the presence of a catalyst consisting essentially of the product of the calcination of a mixture of bismuth nitrate and a heteropoly acid component selected from the group consisting of dodecamolybdoceric acid and ammonium dodecamolybdocerate, and mixtures thereof, wherein the concentration of the bismuth component is about 3% to by weight of the catalyst and wherein the concentration of the said heteropoly acid component is about 3% to 75% by weight of the catalyst.

3. The process according to claim 1 wherein the said mixture also contains from 0.05-2.0 moles of water per mole of propylene.

4. The process according to claim 1 wherein the said oxygen is contained in the said mixture in the form of atmospheric air.

5. The process according to claim 1 wherein the said mixture is in the proportions of 1 mole of the ammonia and 1.5 moles of the oxygen to each mole of propylene, and wherein the said temperature is from 400550 C.

6. The process according to claim 5 wherein the said mixture also contains from 0.252.0 moles of water per mole of propylene and wherein the said oxygen is contained in the said mixture in the form of atmospheric air.

References Cited by the Examiner UNITED STATES PATENTS 2,481,826 9/ 1949 Cosby 260465 .3 2,491,695 12/ 1949 Stiles 260603 2,525,073 10/ 1950 Kimberlin 252475 2,572,300 10/1951 Arnold et al 252467 2,691,037 10/1954 Bellrin'ger et al. 260465.9 2,754,325 7/1956 Smith 260465.9 2,865,868 12/1958 McKinley et al 252467 3,009,943 11/1961 Hadley 260465.3 3,094,552 6/1963 Wood 260465.9

CHARLES B. PARKER, Primary Examiner.

JULIUS GREENWALD, MAURICE A. BRINDISI,

Examiners.

W. BROWN, G. OZAKI, J. P. BRUST,

Assistant Examiners. 

1. A PROCESS FOR PREPARING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACRYLONITRILE AND ACETONITRILE WHICH COMPRISES REACTING A MIXTURE COMPRISING PROPYLENE, AMMONIA AND OXYGEN IN THE PROPORTIONS OF FROM 0.05-10.0 MOLES OF THE AMMONIA AND FROM 0.05-10.0 MOLES OF THE OXYGEN TO EACH MOLE OF THE PROPYLENE, IN VAPOR PHASE AT FROM 300-600*C., IN THE PRESENCE OF A CATALYST CONSISTING ESSENTIALLY OF THE PRODUCT OF THE CALCINATION OF A MIXTURE OF BISMUTH NITRATE AND A HETEROPOLY ACID COMPONENT SELECTED FROM THE GROUP CONSISTING OF DODECAMOLYBDOCERIC ACID AND AMMONIUM DODECAMOLYBDOCERATE, AND MIXTURES THEREOF, WHEREIN THE CONCENTRATION OF THE BISMUTH COMPONENT IS ABOUT 3% TO 75% BY WEIGHT OF THE CATALYST AND WHEREIN THE CONCENTRATION OF THE SAID HETEROPOLY ACID COMPONENT IS ABOUT 3% TO 75% BY WEIGHT OF THE CATALYST AND THEREAFTER SEPARATING THE NITRILE PRODUCTS. 